[DEPRECATED] Use describe_npm_package instead. Get a brief description of an NPM package
AI agents call lookup_npm_doc to retrieve information from MCP Package Docs Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and fetches structured documentation/metadata for NPM packages, which is a read-only query operation. It has no side effects, does not execute code, and does not modify any data. The deprecation status and recommendation to use describe_npm_package instead do not change its security classification.
From the tool's definition Tool description states 'Get a brief description of an NPM package' and is marked [DEPRECATED]. The tool name 'lookup_npm_doc' and verb 'Get' indicate data retrieval without modification or execution.
Documented attack patterns abuse exactly the kind of access lookup_npm_doc gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Package Docs Server, and nothing reaches the server without passing your rules. This is the rule we recommend for lookup_npm_doc:
{
"version": "1",
"default": "deny",
"tools": {
"lookup_npm_doc": {}
}
}lookup_npm_doc is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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[DEPRECATED] Use describe_npm_package instead. Get a brief description of an NPM package. It is categorised as a Read tool in the MCP Package Docs Server MCP Server, which means it retrieves data without modifying state.
Register the MCP Package Docs Server MCP server in PolicyLayer and add a rule for lookup_npm_doc: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches MCP Package Docs Server. Nothing to install.
lookup_npm_doc is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the lookup_npm_doc rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for lookup_npm_doc. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
lookup_npm_doc is provided by the MCP Package Docs Server MCP server (sammcj/mcp-package-docs). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 13 MCP Package Docs Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
13 MCP Package Docs Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.